I don't know about the timing chains in the US, but I guess that they are pretty similar to the ones we use in Europe. You can check whether the original timing chain has been renewed in the past by rotating the engine by hand and look for a black plug link in the chain...the black plug link is the part that is compressed after the chain was renewed (the valve cover has to be removed to check this).

greetingz,

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1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)